gypsum building plaster, Part 1: Excluding premixed lightweight plaster
1976 Edition

Overview of Scope - IS 2547 Part 1

This section defines the physical criteria and testing techniques applicable to gypsum plasters, excluding premixed lightweight varieties.

Essential Clauses & Calculation Methods

• Rounding of Test Data:
  Test outcomes are rounded following IS 2-1960, maintaining the required significant digits.

• Evaluation of Results (Clause 6.4.1):
  For parameters like setting time, transverse strength, and residue on 1.18 mm sieve, calculate average (X) and range (R), then verify compliance using:
  [ X - 0.4R \geq \text{minimum limit} \quad \text{and} \quad X + 0.4R \leq \text{maximum limit} ]

Summary of Physical Requirements (Table 2)

*Strength and mechanical resistance values differ according to plaster type.

flowchart LR
    A[Sample Testing] --> B[Compute Average (X) and Range (R)]
    B --> C{Verify Limits}
    C -->|X - 0.4R >= Min Limit| D[Pass Lower Bound Check]
    C -->|X + 0.4R <= Max Limit| E[Pass Upper Bound Check]

IS 2547 Part 1 - Definitions and Specification Summary

1. Terminology

• Refer to IS 2469-1976 for definitions related to gypsum plasters (Clause 2.1).

2. Assessment of Test Results (Clause 6.4.1)

• Calculate average (X) and range (R) for setting time, transverse strength, and residue on 1.18 mm sieve.
• Confirm compliance with:
  [ X - 0.4R \geq \text{minimum value}, \quad X + 0.4R \leq \text{maximum value} ]

3. Physical Criteria (Clause 5.2, Table 2)

4. Mechanical Resistance

• Indentation diameter limits for neat plaster:
  • Retarded hemihydrate: 3 to 4.5 mm
  • Keene's plaster: ≤ 3.5 mm

5. Rounding Protocol

• Test values are rounded according to IS 2-1960, preserving significant figures as specified.

This summary encapsulates core definitions, formulas, and physical property requirements. For detailed test procedures, refer to IS 2542 (Part 1)-1964.

Gypsum Plaster Classification and Key Criteria per IS 2547 Part 1

1. Basis of Classification:

• Determined by setting time, transverse strength, and residue on 1.18 mm IS sieve.
• Use average (X) and range (R) from test results.
• Calculate:
  [ X + 0.4R \quad \text{and} \quad X - 0.4R ]
• Compliance requires:
  [ X - 0.4R \geq \text{minimum limit}, \quad X + 0.4R \leq \text{maximum limit} ]

2. Rounding Off:

• Follow IS 2-1960 for rounding test outcomes.
• Maintain significant digits as specified.

3. Highlights of Physical Criteria (Table 2):

4. Mechanical Resistance:

• Indentation diameter for neat plaster:
  • Retarded hemihydrate: 3 to 4.5 mm
  • Keene's plaster: ≤ 3.5 mm

flowchart TD
    A[Test Results: Setting time, Strength, Residue] --> B[Calculate Average (X) and Range (R)]
    B --> C[Evaluate X + 0.4R and X - 0.4R]
    C --> D{Check Limits}
    D -->|Complies| E[Pass Classification]
    D -->|Fails| F[Fail Classification]

Chemical Composition Standards for Gypsum Plasters (IS 2547 Part 1)

Summary of Physical Properties (Table 2)

Physical Requirements for Gypsum Plasters (IS 2547 Part 1, Clause 5.2, Table 2)

Notes on Test Result Evaluation (Clause 6.4.1):

• For setting time, transverse strength, and residue, compute average (X) and range (R).
• Confirm: [ X - 0.4R \geq \text{minimum limit} ] [ X + 0.4R \leq \text{maximum limit} ]

Chemical Composition Summary (Clause 4.1, Table 1):

Sampling Guidelines per IS 2547 Part 1

Sampling Instructions

• Packages must be randomly chosen from the lot (Clause 6.2.1).
• Procedures outlined in IS 4905-1968 ensure randomness.

Testing

• Each sample is tested independently per lot to confirm compliance (Clause 6.1.1).
• Results are rounded following IS 2-1960, maintaining specified significant digits.

Sampling Flowchart

flowchart TD
    A[Lot of Packages] --> B[Determine Size of Lot]
    B --> C{Lot Size Range}
    C -->|Up to 100| D[Select 3 Packages]
    C -->|101-150| E[Select 4 Packages]
    C -->|151-300| F[Select 5 Packages]
    C -->|301-500| G[Select 7 Packages]
    C -->|Above 500| H[Select 10 Packages]
    D & E & F & G & H --> I[Random Selection per IS 4905-1968]
    I --> J[Test Each Sample Individually]
    J --> K[Round Results as per IS 2-1960]

Packaging and Marking Guidelines (IS 2547 Part 1)

Packaging (Clause 7.1)

• Gypsum plaster should be dry, free from lumps, and packed in moisture-proof bags or containers.
• Each package must be labeled with:
  • Manufacturer's name
  • Plaster classification and type
  • Manufacture date and batch number if applicable

Sampling for Testing (Clause 6.2 & Table 3)

Marking (Clause 7.2)

• Use of the BIS Standard Mark is regulated under the Bureau of Indian Standards Act, 1986.
• Manufacturers may apply for licensing to utilize the Standard Mark.
• Applying the Standard Mark is optional but encouraged for quality assurance.

Packaging and Marking Process Flow

flowchart TD
    A[Production of Gypsum Plaster] --> B[Ensure Dry, Lump-Free Material]
    B --> C[Pack in Airtight Containers]
    C --> D[Label with Manufacturer and Product Details]
    D --> E[Sample Selection Based on Lot Size]
    E --> F[Conduct Testing on Samples]
    F --> G{Are Test Results Acceptable?}
    G -- Yes --> H[Optionally Mark with BIS Standard]
    G -- No --> I[Reject the Lot]

Criteria for Lot Conformance (IS 2547 Part 1, Clause 6.4)

A lot is deemed conforming when both conditions in Clauses 6.4.1 and 6.4.2 are fulfilled:

1. Statistical Compliance (Clause 6.4.1)

• For parameters such as setting time, transverse strength, and residue on 1.18 mm sieve:
  • Calculate average (X) and range (R).
  • Verify: [ X - 0.4R \geq \text{minimum limit} ] [ X + 0.4R \leq \text{maximum limit} ]
  • Both criteria must be satisfied.

2. Rounding Off (per IS 2-1960)

• Test results should be rounded to the decimal places specified in the standard.

Summary of Physical Parameters (Table 2, Clause 5.2)

Conformity Evaluation Flow

flowchart TD
    A[Start: Test Gypsum Plaster Lot] --> B[Calculate Average (X) and Range (R)]
    B --> C[Check if X - 0.4R ≥ Min Limit]
    B --> D[Check if X + 0.4R ≤ Max Limit]
    C & D --> E{Both Conditions Met?}
    E -- Yes --> F[Lot Conforms]
    E -- No --> G[Lot Does Not Conform]

Procedure for Determining Soluble Sodium and Magnesium Salts (IS 2547 Part 1)

Testing Method Summary (Clause A-1.1)

• Weigh 1 g of gypsum plaster, ground to pass a 212-micron IS sieve.
• Place in a polyethylene bottle with 100 ml water and 1 g salt-free gypsum.
• Shake intermittently over 1 hour to prevent caking.
• Allow solids to settle; clear supernatant liquid is collected.
• Analyze the supernatant to quantify soluble sodium and magnesium salts.

Expression of Results

• Sodium salts reported as Na2O %
• Magnesium salts reported as MgO %

Chemical Requirements Extract (Table 1)

This test ensures gypsum plaster purity and quality by limiting soluble salt content.

Determining Loss on Ignition (LOI) for Gypsum Plaster (IS 2547 Part 1)

• LOI represents the percentage weight loss when a sample is heated to a specified temperature, indicating moisture, volatile substances, and carbonates.

• LOI Limits (% by mass) from Table 1 (Clause 4.1):

• Refer to Appendix B of IS 2547 Part 1 for the detailed testing procedure.

Calculations (Clause 6.4.1)

• Calculate average (X) and range (R) for LOI test results.
• Confirm: [ X - 0.4R \geq \text{minimum limit} ] [ X + 0.4R \leq \text{maximum limit} ]

Additional Chemical Limits

• Soluble magnesium salts (as MgO): max 0.3%
• Soluble sodium salts (as Na2O): max 0.3%

Summary

• LOI measures impurities and moisture content.
• It must fall within specified limits to ensure plaster quality.
• Use average and range calculations for test validation.

flowchart LR
    A[Prepare Sample] --> B[Weigh Sample]
    B --> C[Heat to Specified Temperature]
    C --> D[Cool and Weigh Residue]
    D --> E[Calculate LOI = ((Initial - Final) / Initial) × 100]
    E --> F{Check if Within Limits}
    F -->|Yes| G[Accept Sample]
    F -->|No| H[Reject Sample]

IS 2547 Part 1: Method for Measuring Free Lime in Gypsum Plaster

Key Specification

• Minimum free lime content for Retarded Hemihydrate Gypsum Plaster: ≥ 3% (Clause 4.1, Table 1)

Chemical Composition Extract (Table 1)

Testing Procedure (Appendix C)

• Weigh 5 g of the plaster sample.
• Titrate with 0.5 N hydrochloric acid (HCl).
• 1 ml of 0.5 N HCl corresponds to 0.37% Ca(OH)₂ free lime.

Calculation Formula:

[ \text{Free Lime %} = \frac{\text{ml of HCl used} \times 0.37}{\text{sample weight (g)}} \times 100 ]

Summary Steps:

1. Accurately weigh 5 g of plaster.
2. Titrate with standardized 0.5 N HCl solution.
3. Calculate free lime percentage using the formula.
4. Confirm free lime content meets or exceeds 3% for retarded hemihydrate plaster.

This procedure ensures gypsum plaster durability and adherence to IS 2547 Part 1.